1. Field of the Invention
The present invention relates to an electroluminescence display unit formed by connecting a plurality of electroluminescence display panels to each other and a method of fabricating the same.
2. Description of the Prior Art
In general, a CRT (cathode-ray tube), a PDP (plasma display panel), a liquid crystal projector and the like are developed as large-sized display units. When these display units are increased in size, however, the CRT has heavy weight, the PDP also has heavy weight although the weight is smaller than that of the CRT, and the liquid crystal projector has low luminance and low resolution.
On the other hand, a thin and lightweight liquid crystal display unit having none of the aforementioned problems is increasingly developed in size. In order to increase the size of the liquid crystal display unit, a structure obtained by pasting a plurality of small panels to each other or a structure obtained by forming one of a pair of electrodes on a large-sized substrate with a wire connection part for an external circuit or the like while pasting the other electrode with a small substrate is mainly employed. However, the junction defining a non-display part such as a liquid crystal sealing part is conspicuous in the former structure while it is difficult to control a space for filling liquid crystals in the latter structure, leading to irregular display in both cases. Further, the liquid crystal display unit employing non-luminescent liquid crystals is a photoreceptor type display unit requiring a light source. Therefore, the liquid crystal display unit disadvantageously has viewing angle dependency, hardly attains high luminance, and has a low contrast.
Under such circumstances, an electroluminescence (hereinafter abbreviated as EL) display unit is watched with interest as a self-luminescent display unit, and an organic EL display unit employing an organic thin film formed on a glass substrate as an emission layer is particularly noted as a thin and lightweight display unit similarly to the liquid crystal display unit. The organic EL display unit may also be increased in size through a structure obtained by forming elements on a large-sized substrate or a structure obtained by pasting a plurality of small panels to each other, similarly to the liquid crystal display unit.
In the former structure, however, it is difficult to increase the size of a substrate formed with TFTs (thin-film transistors) as switching elements for respective elements or to uniformly form an organic EL emission layer on the overall surface of a large-sized substrate, disadvantageously leading to irregular luminance. In the latter structure, the junction between the plurality of small panels merely pasted to each other is conspicuous to result in a non-uniform display screen although irregular luminance can be reduced. While Japanese Patent Laying-Open No. 5-205875 (1993), for example, discloses a method of connecting small panels and electrically connecting adjacent ones of the small panels with each other in order to increase the size of an organic EL display unit, this gazette discloses no method of rendering the junction between the small panels inconspicuous.
In relation to the liquid crystal display unit, on the other hand, there is reported a method of defining a single pixel by three display dots of R (red), G (green) and B (blue) and matching the distance between pixels located on ends of adjacent small panels with the width of black stripes in order to render the junction between small panels inconspicuous (Sharp Giho No. 69, December 1997, pp. 81-84). However, this method is specific to a liquid crystal display unit sealing ends of panels for preventing leakage of liquid crystals with long distances between pixels located on ends of the panels and the ends of the panels, and cannot be directly applied to an EL display unit requiring no such sealing.
An object of the present invention is to provide an electroluminescence display unit capable of rendering the junction between adjacent ones of a plurality of electroluminescence display panels inconspicuous when the electroluminescence display panels are connected to each other for forming a single display unit and a method of fabricating the same.
Another object of the present invention is to provide an electroluminescence display unit capable of rendering the junction between adjacent ones of a plurality of electroluminescence display panels inconspicuous without deteriorating emission parts when the electroluminescence display panels are connected to each other for forming a single display unit and a method of fabricating the same.
According to an aspect of the present invention, an electroluminescence display unit is formed by connecting a plurality of electroluminescence display panels to each other, while each of the plurality of electroluminescence display panels is formed with a plurality of emission parts arranged along a first direction at a first pitch and emission parts opposed to each other through the junction between the electroluminescence display panels adjacent to each other along the first direction are arranged at a second pitch equal to the first pitch.
In the electroluminescence display unit, the plurality of emission parts are arranged on each of the plurality of electroluminescence display panels in the first direction at the first pitch, while the emission parts opposed to each other through the junction between the electroluminescence display panels adjacent to each other along the first direction are arranged at the second pitch equal to the first pitch.
The electroluminescence display panels can be formed in the aforementioned manner since the electroluminescence display panels store no liquid crystals requiring sealing dissimilarly to the liquid crystal display unit and hence the distance between emission parts located on endmost portions of the panels and ends of the panels can be extremely reduced as compared with the liquid crystal display unit. In other words, the present invention has been proposed by noting the features of the aforementioned electroluminescence display panels and reducing the distance between the emission parts located on the endmost portions of the panels and the ends of the panels for arranging the emission parts adjacent to each other over the panels also at the pitch equal to the pitch for those located on the panels.
Therefore, it follows that not only the emission parts located on the panels but also the emission parts adjacent to each other over the panels are arranged at the same pitch, whereby the emission parts are arranged on the overall display unit at a constant pitch. Also when connecting a plurality of electroluminescence display panels to each other for forming a single display unit, therefore, the junction between adjacent ones of the electroluminescence display panels can be rendered inconspicuous.
The second pitch is preferably within xc2x120% of the first pitch. In this case, fabrication variations in component size can be allowed to some extent within a range not rendering the junction conspicuous, whereby fabrication steps are simplified.
The plurality of emission parts preferably include a plurality of color emission parts emitting light of different colors, the plurality of color emission parts are preferably arranged on each of the plurality of electroluminescence display panels along the first direction at the first pitch, and the color emission parts opposed to each other through the junction between the electroluminescence display panels adjacent to each other along the first direction are preferably arranged at the second pitch.
In this case, the color emission parts enable color display such as full-color display, and it follows that not only the color emission parts located on the panels but also those adjacent to each other over the panels are arranged at the same pitch, so that the color emission parts are arranged at a constant pitch on the overall display unit. Also when connecting a plurality of electroluminescence display panels to each other for forming a single display unit and performing color display with the color emission parts, therefore, the junction between adjacent electroluminescence display panels can be rendered inconspicuous.
Each of the plurality of emission parts may include a plurality of color emission parts emitting light of different colors, the color emission parts may be arranged in the emission part along the first direction at a third pitch, and the distance between the emission parts opposed to each other through the junction between the electroluminescence display panels adjacent to each other along the first direction may be set to integral times the third pitch.
In this case, the color emission parts enable color display such as full-color display while it follows that not only pixels located on the panels but also those adjacent to each other over the panels are arranged at the same pitch when regarding each of the plurality of color emission parts, i.e., each emission part as a single pixel, so that the pixels are arranged at a constant pitch on the overall display unit. Also when connecting a plurality of electroluminescence display panels to each other for forming a single display unit and performing color display with the color emission parts, therefore, the junction between adjacent ones of the electroluminescence display panels can be rendered inconspicuous.
The plurality of emission parts preferably include a plurality of blue emission parts emitting blue light and a plurality of red emission parts emitting red light, and the junction between the electroluminescence display panels adjacent to each other along the first direction is preferably arranged between the blue emission parts and the red emission parts.
In this case, the junction is arranged between the blue emission parts and the red emission parts having large heating values in emission, whereby moisture permeating through the junction can be evaporated by the blue emission parts and the red emission parts. Thus, permeation of moisture from the junction can be suppressed, thereby improving reliability of the electroluminescence display panels.
The junction between the electroluminescence display panels adjacent to each other along the first direction is preferably located closer to an emission part having lower luminance in white emission among the emission parts opposed to each other through the junction. In this case, the junction between the panels is located closer to the emission part having lower luminance in white emission, whereby the junction is rendered further inconspicuous and excellent display quality can be implemented.
A width adjusting member adjusting the width of the junction between the electroluminescence display panels adjacent to each other along the first direction is preferably arranged on the junction. In this case, the width adjusting member can precisely set the width of the junction, whereby the pitch between the emission parts adjacent to each other over the panels can be precisely matched with the pitch between the emission parts located on the panels.
The width adjusting member preferably includes spherical particles having a constant particle size mixed into an adhesive bonding the electroluminescence display panels adjacent to each other along the first direction. In this case, the width of the junction can be precisely set by adjusting the particle size of the spherical particles mixed into the adhesive while the panels can be bonded to each other by the adhesive with sufficient strength.
The plurality of emission parts are preferably arranged on each of the plurality of electroluminescence display panels along a second direction intersecting with the first direction at a prescribed pitch, and emission parts opposed to each other through the junction between the electroluminescence display panels adjacent to each other along the second direction are preferably arranged at the aforementioned prescribed pitch.
In this case, it follows that not only the emission parts located on the panels but also those adjacent to each other over the panels are two-dimensionally arranged at the same pitch so that all junctions between adjacent electroluminescence display panels can be rendered conspicuous also when forming a single display unit by connecting the plurality of electroluminescence display panels.
Each of the plurality of electroluminescence display panels preferably includes a plurality of first electrode layers and a plurality of second electrode layers arranged on a first substrate to intersect with each other, the emission parts are preferably provided on intersections between the plurality of first electrode layers and the plurality of second electrode layers, the plurality of first electrode layers are preferably made of a metal oxide, the plurality of second electrode layers are preferably made of a metal, and end surfaces of the plurality of second electrode layers are preferably inwardly separated from a side edge of the first substrate closer to the junction between the plurality of electroluminescence display panels on the side of the junction.
In this case, the end surfaces of the plurality of second electrode layers are inwardly separated from the side edge of the first substrate closer to the junction between the plurality of electroluminescence display panels on the side of the junction, whereby a sufficient distance can be secured between the junction surfaces of the electroluminescence display panels formed by working and the end surfaces of the second electrode layers made of a metal. Thus, the second electrode layers are prevented from oxidization caused by influence of moisture penetrating through the junction between the electroluminescence display panels when the junction surfaces are worked and from separation along the interface between the same and the emission parts. Consequently, deterioration of the second electrode layers can be reduced, while reduction of the characteristics of the emission parts can be prevented when working the junction surfaces.
Also as to the appearance, no second electrode layer of a metal is present around the junction and hence metallic luster is suppressed in the vicinity of the junction so that a feeling of wrongness can be reduced around the junction. Consequently, the junction between the adjacent electroluminescence display panels is rendered inconspicuous.
Each of the plurality of electroluminescence display panels may further include a sealing layer covering the plurality of first electrode layers, the plurality of second electrode layers and the emission parts on the first substrate.
In this case, the sealing layer is interposed between the junction surfaces of the first substrate and end surfaces of the second electrode layers, whereby deterioration of the second electrode layers can be further reduced while reduction of characteristics of the emission parts can be further prevented when working the junction surfaces.
End surfaces of the plurality of second electrode layers preferably do not extend beyond outer side surfaces of the first electrode layers in the vicinity of the junction between the plurality of electroluminescence display panels toward the side of the junction on the side of the junction.
In this case, a further sufficient distance can be secured between the junction surfaces of the display panels formed by working and the end surfaces of the second electrode layers made of a metal. Thus, deterioration of the first electrode layers caused by penetration of moisture can be remarkably reduced while reduction of the characteristics of the emission parts can be further sufficiently prevented when working the junction surfaces.
Also as to the appearance, the end surfaces of the plurality of second electrode layers do not extend beyond the outer side surfaces of the first electrode layers in the vicinity of the junction between the display panels, whereby metallic luster is suppressed in a region along the junction between the adjacent display panels and a feeling of wrongness can be further reduced around the junction. Consequently, the junction between the adjacent display panels is rendered further inconspicuous.
The emission parts may include emission layers made of an organic material or an inorganic material. In this case, an organic or inorganic electroluminescence display unit having a large area is implemented with an inconspicuous junction between adjacent electroluminescence display panels. When the emission parts include emission layers made of an organic material, the emission layers made of an organic material readily influenced by moisture in particular are prevented from deterioration when working the junction surfaces of the electroluminescence display panels.
Each of the plurality of electroluminescence display panels may further include a second substrate opposed to the first substrate to hold the plurality of first electrode layers, the plurality of second electrode layers and the emission parts therebetween.
In this case, the first electrode layers, the second electrode layers and the emission parts are prevented from damage caused by a holder supporting the display panels when working the junction surfaces of the display panels.
Each of the plurality of electroluminescence display panels may be a passive electroluminescence display panel or an active electroluminescence display panel. In this case, a passive or active electroluminescence display unit having a large area is implemented with an inconspicuous junction between adjacent electroluminescence display panels.
According to another aspect of the present invention, a method of fabricating an electroluminescence display unit formed by connecting a plurality of electroluminescence display panels to each other comprises steps of forming the plurality of electroluminescence display panels by providing a plurality of emission parts arranged along a first direction at a first pitch and connecting opposite ends of the electroluminescence display panels adjacent to each other along the first direction through a width adjusting member so adjusted that emission parts opposed to each other through the junction between the electroluminescence display panels adjacent to each other along the first direction are arranged at a second pitch equal to the first pitch.
According to the method of fabricating an electroluminescence display unit, the panels are connected to each other through the width adjusting member, whereby the interval between the panels can be readily adjusted with the width adjusting member so that the second pitch is equal to the first pitch. Therefore, an electroluminescence display unit precisely matching the pitch between emission parts adjacent to each other over panels with the pitch between those located on the panels can be readily manufactured.
The width adjusting member is preferably formed by spherical particles having a constant particle size, and the connecting step preferably includes a step of mixing the spherical particles into an adhesive while adjusting the particle size of the spherical particles so that the second pitch is equal to the first pitch and bonding opposite ends of adjacent electroluminescence display panels to each other with the adhesive.
In this case, the adhesive mixed with the spherical particles is applied to bonded surfaces of the panels and proper pressure is applied thereto for aligning the spherical particles with each other between the panels. Therefore, the particle size of the spherical particles defines the width of the junction, which can be precisely adjusted through the spherical particles having a homogeneous particle size. Consequently, bonding between the panels and adjustment of the junction between the panels can be simultaneously performed for simplifying the fabrication steps.
The step of forming the plurality of electroluminescence display panels preferably further includes steps of forming a plurality of first electrode layers and a plurality of second electrode layers arranged on each of a plurality of substrates to intersect with each other while providing the emission parts on intersections between the plurality of first electrode layers and the plurality of second electrode layers and forming end surfaces of the plurality of second electrode layers on positions inwardly separated from side edges of the substrates closer to the junction between the plurality of electroluminescence display panels and working an end of each electroluminescence display panel thereby forming a junction surface on each electroluminescence display panel.
In this case, the end surfaces of the plurality of second electrode layers are inwardly separated from the side edge of the substrate closer to the junction between the electroluminescence display panels on the side of the junction, whereby a sufficient distance can be secured between the junction surfaces of the electroluminescence display panels formed by working and the end surfaces of the second electrode layers made of a metal. Thus, the second electrode layers are prevented from oxidization caused by influence of moisture penetrating through the junction surfaces of the electroluminescence display panels when the junction surfaces are worked and from separation along the interfaces between the same and the emission parts. Consequently, deterioration of the second electrode layers can be reduced, while reduction of the characteristics of the emission parts can be prevented when working the junction surfaces.
Also as to the appearance, no second electrode layer of a metal is present around the junction and hence metallic luster is suppressed in the vicinity of the junction so that a feeling of wrongness can be reduced around the junction. Consequently, the junction between the adjacent electroluminescence display panels is rendered inconspicuous.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.